Chang Joonho, Choi Bori, Tjolleng Amir, Jung Kihyo
Department of Industrial and Manufacturing Engineering, Pennsylvania State University, University Park, PA 16802, USA.
University of Ulsan, 93 Daehak-ro, Nam-gu, Ulsan, 680-749, Republic of Korea.
Appl Ergon. 2017 Apr;60:282-292. doi: 10.1016/j.apergo.2016.12.008. Epub 2016 Dec 27.
Intensive use of the thumbs for text entry on smartphones may contribute to discomfort, pain, or musculoskeletal disorders. This study investigated the effect of twenty-five button positions (5 rows × 5 columns) on a soft keyboard for two-thumb entry. Two experiments measured muscle activity, touch time, and discomfort as a function of the button positions. In Phase I, the muscle activities of two intrinsic (abductor pollicis brevis and first dorsal interossei) and two extrinsic (abductor pollicis longus and extensor digitorum communis) muscles associated with thumb motions were observed for ten college students (age: 24.2). In Phase II, touch time and discomfort were measured for 40 college students (age: 23.6). The results demonstrated that the %MVCs of the intrinsic muscles significantly increased when the thumbs flexed and abducted. Also, the button positions near the rest positions of the thumbs resulted in significantly shorter touch times (0.66 s) and lower discomfort ratings (0.70 pt) than their peripheral buttons (0.76 s; 2.29 pt).
在智能手机上频繁使用拇指进行文本输入可能会导致不适、疼痛或肌肉骨骼疾病。本研究调查了二十五种按钮位置（5行×5列）对用于双拇指输入的软键盘的影响。两项实验测量了肌肉活动、触摸时间以及作为按钮位置函数的不适感。在第一阶段，观察了十名大学生（年龄：24.2岁）与拇指运动相关的两块内在肌（拇短展肌和第一背侧骨间肌）和两块外在肌（拇长展肌和指总伸肌）的肌肉活动。在第二阶段，对40名大学生（年龄：23.6岁）测量了触摸时间和不适感。结果表明，当拇指弯曲和外展时，内在肌的最大自主收缩百分比显著增加。此外，拇指静止位置附近的按钮位置导致的触摸时间（0.66秒）明显短于其周边按钮（0.76秒），不适感评分（0.70分）也低于周边按钮（2.29分）。
